1. Field of the Invention
The present invention relates to an engine start control system which is convenient when used for manually starting an engine with the aid of a recoil starter or the like.
2. Description of the Related Art
Some types of engines used for outboard motor employ an ECM (Engine Control Module) for controlling fuel injection by an injector. The ECM in this case is configured to use the atmospheric pressure as one parameter for regulating the fuel injection.
Patent Document 1 discloses a configuration aimed at detecting the atmospheric pressure without using the atmospheric pressure sensor, wherein the atmospheric pressure is detected by a pressure sensor for detecting air pressure in an intake pipe, based on a pressure detection signal of the pressure sensor detected when the control unit (ECM) is powered ON, while a crankshaft stays still.
In particular, marine vessels hardly encounter a situation such that the atmospheric pressure sharply changes (for example, travel towards highlands) in a single operation, so that information of the atmospheric pressure only at the start of operation will suffice. Accordingly, there will be no need of equipping a dedicated atmospheric pressure sensor, if the atmospheric pressure may be known from the pressure in the intake pipe as described in Patent Document 1, and this will give a large cost merit. [Patent Document 1] Japanese Laid-Open Patent Publication No. H11-247706
The configuration described in Patent Document 1 is, however, premised on installing a battery. In a configuration without the battery, the ECM will be activated as powered from a generator which operates in association with rotation of a crankshaft of the engine. In other words, the ECM will not be activated unless the crankshaft rotates, so that it is unable to detect the atmospheric pressure based on the pressure detection signal of the pressure sensor, when the crankshaft stays still, as described in Patent Document 1.
For the configuration without the battery, there is now one possible idea of determining the atmospheric pressure, by detecting the maximum value of pressure in the intake pipe, when the ECM is powered from the manually-cranked generator at the starting using the recoil starter. In the manually cranking, that is, in a period before the engine starts to rotate under its own power, the pressure in the intake pipe becomes negative relative to the atmospheric pressure in the intake process, and peaks at the time of switching from the exhaust process to the intake process, showing the maximum value almost coincides with the atmospheric pressure.
By the way, electric power generation by the generator sharply decreases when engine speed decreases particularly in low speed region. The engine speed also decreases in the compression process. For this reason, only with a weak force of pulling of the recoil starter, the ECM would once activate as powered from the manually cranked generator, but would stop in the compression process since the power generation would decrease due to lowered engine speed. On the other hand, even under such extremely low speed, the engine restarts if combustion occurs (first explosion) in a specified timing beyond the compression dead top center. As a consequence, the power generation of the generator elevates again, and the ECM reactivates. As described in the above, an event encountered herein is that the ECM is once activated, then stops, and is reactivated as triggered by first explosion. In this specification, the event will be referred to as “instantaneous interruption and reactivation” of ECM, hereinafter.
For the case where the instantaneous interruption and reactivation of ECM occurs, the reactivated ECM will determine the atmospheric pressure by detecting a maximum value of pressure in the intake pipe after the engine began to rotate under its own power. However, after the engine began to rotate under its own power, the pressure in the intake pipe, and even the maximum value thereof, becomes negative relative to the atmospheric pressure, showing no agreement with the atmospheric pressure.